1. Field of the Invention
The present invention relates to a purging device and a purging method for a stocker or the like, and in particular to one which monitors oxygen concentrations in the purging device.
2. Description of the Related Art
In semiconductor factories, articles such as semiconductor wafers or reticles are accommodated in a container such as a FOUP, and the container is stored in a stocker. Stockers encompass a purge stocker in which purging is performed with a purge gas such as a nitrogen gas (Patent Literature 1: JP 2012-248785). In the purge stocker, each cell of the stocker is provided with a purge gas nozzle, and by putting the nozzle in contact with a gas inlet hole of a container such as a FOUP, a purge gas is blown into the container. The blown-in purge gas is discharged from the container to the inner space or the like of the purge stocker. Clean air is blown into the purge stocker from its ceiling part, and is discharged from its underfloor and the like, and thus the oxygen concentration of the inner space of the purge stocker depends on the relationship between discharge of the purge gas from the containers and the flow of the air from the ceiling part.
A conventional technique relating to a purging device will be described. Patent Literature 2 (WO00/31780) discloses that two types of purge gases, namely, an inert gas and clean dry air are supplied; when a worker enters the purging device under consideration for maintenance or the like, the purge gas is switched to the clean dry air, and otherwise purging is regularly performed with the inert gas.